I have some problems with movie metadata. I have locked metadata but after update titles of some movis changed. It is repeating at some movies ( about 10 from 1000) again and again, the others are OK. Thanks for advices.
Probably because your naming schema is not conforming to Plex standards and every time it scans it is trying to match again and again, thus loosing any manual edits you make. Correct your naming convention and the movies will match on their own and grab the correct meta data, negating any manual overrides.
https://support.plex.tv/articles/200381023-naming-movie-files/
see also


